Vital Ruby my_each

x.rb

class Array

  def my_each
    i = 0
    while i < self.length
      yield self[i]
      i += 1
    end
    self[0]
  end

  def my_map
    result = []
    each do |item|
      result << yield(item)
    end
    result
  end

  def my_inject(initial=nil)
    acc = initial
    my_each do |item|
      if acc.nil?
        acc = item
      else
        acc = yield(acc, item)
      end
    end
    acc
  end

end

describe "My Array Methods" do
  let(:array) { [1,2,3,4] }

  describe "#my_each" do

    it "iterates over each item" do
      sum = 0
      array.my_each do |item| sum += item end
      sum.should == 10
    end
  end

  describe "#my_map" do
    it "maps each value to a new value" do
      result = array.my_map { |item| item * 2 }
      result.should == [2,4,6,8]
    end
  end

  describe "#my_inject" do
    context "with an explicit initial" do
      it "injects an operation in the array" do
        result = array.my_inject(0) { |acc, item| acc + item }
        result.should == 10
      end
    end

    context "with an implicit initial" do
      it "injects an operation in the array" do
        result = array.my_inject { |acc, item| acc + item }
        result.should == 10
      end
    end
  end
end